Isoform Nell-1 peptide

ABSTRACT

This application generally relates to an isoform Nell-1 peptide, compositions thereof, and methods of using the same.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

This invention was made with Government support under Grant No. DE016107 awarded by the National Institute of Health. The Government has certain rights in this invention.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase application under 35 U.S.C. §371(c) of International Application No. PCT/US10/28540, filed on Mar. 24, 2010, which claims the benefit of U.S. Provisional Application No. 61/163,297 filed on Mar. 25, 2009, the teaching of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

There are many situations where bone formation and regeneration are required for treatment, e.g., alveolar bone grafting, craniofacial distraction osteogenesis, spinal fusion, segmental long bone defects.

Defects in the process of bone formation and regeneration are linked to the development of several human diseases and disorders, e.g. osteoporosis and osteogenesis imperfecta. Failure of the bone repair or cartilage repair mechanism is also associated with significant complications in clinical orthopedic practice, for example, fibrous non-union following bone fracture, implant interface failures and large allograft failures. The lives of many individuals would be improved by the development of new therapies designed to stimulate and strengthen the fracture repair process.

Any new technique to stimulate bone repair or cartilage repair would be a valuable tool in treating bone fractures. A significant portion of fractured bones are still treated by casting, allowing natural mechanisms to effect wound repair. Although there have been advances in fracture treatment in recent years, including improved devices, the development of new processes to stimulate or complement the wound repair mechanisms would represent significant progress in this area.

The techniques of bone reconstruction, such as used to reconstruct defects occurring as a result of trauma, cancer surgery or errors in development, would be improved by new methods to promote bone repair. Reconstructive methods currently employed, such as using autologous bone grafts or bone grafts with attached soft tissue and blood vessels, are associated with significant drawbacks of both cost and difficulty. For example, harvesting a useful amount of autologous bone is not easily achieved, and even autologous grafts often become infected or suffer from resorption.

Readily available and reliable bone graft material is essential for many orthopedic surgeries. The current gold standard for bone graft material is autologous bone. However associated donor site morbidity including pain, gait disturbance, thigh paresthesia for iliac crest donor sites, infection, neurologic deficits, and hematomas for calvarial grafts make autograft harvest less than ideal. Thus, there is a need for better autograft alternatives.

Efforts to influence bone repair using bone stimulating proteins and peptides, e.g., bone morphogenic proteins (BMPs), resulted in only limited success. While BMP2 is FDA approved and clinically successful as an osteoinductive biologic, there are significant reported side effects including life-threatening cervical swelling. Therefore there is need to develop improved and safer therapeutic approaches.

Cartilage is a type of dense connective tissue. It is composed of chondrocytes which are dispersed in a firm gel-like matrix. Cartilage is avascular (contains no blood vessels) and nutrients are diffused through the matrix. Cartilage is found in the joints, the rib cage, the ear, the nose, the throat, and between intervertebral disks.

Cartilage can be damaged by wear, injury, or diseases. As aging progresses, the water and protein content of the body's cartilage changes. This change results in weaker, more fragile and thin cartilage. Osteoarthritis is a common condition of cartilage failure that can lead to limited range of motion, bone damage and invariably pain. Due to a combination of acute stress and chronic fatigue, osteoarthritis directly manifests itself in a wearing away of the articulating surface and, in extreme cases, bone can be exposed in the joint. In another example, loss of the protective stabilizing meniscus leads to increased joint laxity or abnormal motions that lead to joint instability. The excessive motion and narrowed contact area promotes early arthritic changes.

Although numerous methods have been described for treatment of cartilage problems, it is clear that many are artificial or mechanically based solutions that do not seek to recreate normal cartilage tissue biology. Therefore, there is a need for methods for stimulating cartilage formation and repair.

Efforts have been continuously made to find better or alternative osteoinductive agents and therapeutic approaches in treating bone related and cartilage related conditions.

SUMMARY OF THE INVENTION

This invention provides an isoform Nell-1 (ISN-1) peptide and methods of making the isoform Nell-1 peptide.

In various embodiments, this invention provides a composition or a bone graft for enhancing the bone formation in a subject in which it is implanted. In some embodiments, the composition contains a biocompatible matrix and an ISN-1 peptide, a related agent, or combination thereof. The composition can further comprise LNell-1 protein, a related agent, or a combination thereof.

In some embodiments, the composition can be a pharmaceutical composition which comprises a suitable carrier or excipient. In some embodiments, the pharmaceutical composition can be formulated into suitable formulation for suitable route of administration.

In some embodiments, the composition can be a bone graft which contains a biocompatible matrix and an ISN-1 protein, a related agent, a cell expressing an ISN-1 protein, or a combination thereof. In some embodiments, the graft material is resorbable or biodegradable. In some embodiments, the graft material can be synthetic or naturally occurring (e.g., allograft). The matrix can include a biodegradable polymer. The matrix can be impregnated with an ISN-1 protein or a related agent, a cell expressing an ISN-1 protein or a related agent, or a combination thereof. The bone graft material can further comprise LNell-1 protein or a related agent, a cell expressing LNell-1 protein or a related agent, or a combination thereof.

In various embodiments, this invention provides a method of increasing bone formation or regeneration. The method can be used for the repair of bone fractures. The method comprises increasing concentration of an ISN-1 gene product at or near the fracture site. In some embodiments, the method comprises introducing an osteogenic cell or bone precursor cell that over expresses ISN-1 into the fracture site. In some embodiments, the method comprises increasing the expression of ISN-1 gene product in an osteogenic cell or bone precursor cell at or near the site of the bone fracture.

In some embodiments, the fracture site is contacted with an ISN-1 protein or a pharmaceutical composition thereof. The fracture site can be contacted with LNell-1 protein in addition to the ISN-1 protein.

In various embodiments, this invention provides a method of treating osteoporosis using an ISN-1, a related agent, or a composition thereof.

In various embodiments, this invention provides a method for inducing cartilage formation or repair using an ISN-1, a related agent, or a composition thereof. The composition can include an ISN-1 or related agent, and optionally at least one other active agent, cells, and biocompatible material implanted for the purpose of cartilage repair (i.e., hyaline cartilage, elastic cartilage, or fibrocartilage).

In various embodiments, the use of ISN-1 can be combined with the use of LNell-1.

In various embodiments, this invention provides a method of expressing a functional ISN-1 peptide in a cell, said method comprising providing a nucleic acid construct including at least a nucleic acid encoding at least an ISN-1 peptide in frame with a nucleic acid encoding a secretory signal peptide; transfecting a cell with said nucleic acid construct; culturing said cell under conditions that permit expression of the ISN-1 peptide; optionally collecting ISN-1 peptide secreted from the cell line; optionally substantially purifying the ISN-1 peptide; and optionally testing the activity of the ISN-1 peptide to induce bone formation.

Related cell line and nucleic acid construct for expressing ISN-1 are also provided.

In the aforementioned embodiments, the ISN-1 protein can be SNell-1 protein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows schematic comparison of TSP-1 with LNell-1 and SNell-1 proteins.

FIG. 2 shows LNell-1 and SNell-1 expression after Osx and Runx2 transfection in NMCCs. Mouse primary cells were transfected with control (Con), Osx and Runx2 plasmids. 48 hours after transfection, RNA samples were extracted for RT-PCR and medium collected for immunoprecipitation (IP) assay using Nell-1 C-terminal Ab crosslinked with protein G beads. (A) RT-PCR results after using LNell-1 or SNell-1 primers. (B) IP results using C-terminal Nell-1 antibody recognizing both LNell-1 and SNell-1.

FIG. 3 shows the effects of LNell-1 and SNell-1 on Runx2, Osx, Oc expression and mineralization.

FIG. 4 shows LNell-1 and SNell-1 protein express patterns in mice heads.

FIG. 5 shows calvarial defect healing with SNell-1.

FIG. 6A shows sequence of SNell-1 protein [Homo sapiens] (SEQ ID NO:1).

FIG. 6B shows sequence of SNell-1 DNA (CDS) [homo sapiens] (SEQ ID NO:2).

FIG. 7A shows sequence of LNell-1 protein [Homo sapiens] ((SEQ ID NO:3).

FIG. 7B shows sequence of LNell-1 DNA (CDS) [homo sapiens] (SEQ ID NO:4).

DETAILED DESCRIPTION

The present invention provides an isoform Nell-1 peptide (generally referred as ISN-1 herein). The previously discovered Nell-1 peptide of 810 amino acids is referred to as LNell-1 herein. One exemplary ISN-1 is a short peptide referred to as SNell-1 herein.

DEFINITION

As used herein, the term “ISN-1” refers to a Nell-1 peptide where the TSP1-N [N-terminal thrombospondin-1 (TSP-1)-like domain present in Nell-1 peptide is removed so as to be a peptide retaining the function of Nell-1 having a molecular weight about 63 kD. Physical advantages of a peptide having a lower molecular weight include, e.g., enhanced efficiency of delivery into a cell, ease of upstream process development—more efficient cell synthesis or secretion into media, ease of downstream process development—more efficient separation, purification, folding, etc. Biological advantages include increased osteogenic differentiation as evidenced by increased expression of osteoblastic differentiation markers Runx2, Osx, and Oc (FIG. 3) and bone formation.

The term “osteogenic cells” refers to cells capable of mineralizing. Osteogenic cells include osteoblasts, osteoblast like cells, mesenchymal cells, fibroblast cells, fetal embryonic cells, stem cells, bone marrow cells, dura cells, chrondrocytes, and chondroblastic cells.

As used herein, the term “bone precursor cells” refers to the cells that can differentiate into osteoblasts upon exposure to a bone growth factor and deposit calcium into the extracellular matrix.

As used herein, the term “bone progenitor cells” refers to any or all of those cells that have the capacity to ultimately form, or contribute to the formation of, new bone tissue. This includes various cells in different stages of differentiation, such as, for example, stem cells, bone marrow cells, fibroblasts, vascular cells, osteoblasts, chondroblasts, osteoclasts, and the like. Bone progenitor cells also include cells that have been isolated and manipulated in vitro, e.g. subjected to stimulation with agents such as cytokines or growth factors or even genetically engineered cells. The particular type or types of bone progenitor cells that are stimulated using the methods and compositions of the invention are not important, so long as the cells are stimulated in such a way that they are activated and, in the context of in vivo embodiments, ultimately give rise to new bone tissue.

The term “osteochondroprogenitor” refers to any cell capable of forming cartilage, e.g., less differentiated osteogenic cells which are capable of mineralizing and/or forming cartilage. Osteochondroprogenitor cells include osteoblasts, osteoblast like cells, mesenchymal cells, fibroblast cells, fetal embryonic cells, stem cells, bone marrow cells, dura cells, chrondrocytes, and chondroblastic cells.

The term “osteoporosis” refers to a heterogeneous group of disorders characterized by decreased bone mass and fractures. Clinically, osteoporosis is segregated into type I and type II. Type I osteoporosis occurs predominantly in middle aged women and is associated with estrogen loss at the menopause, while osteoporosis type II is associated with advancing age.

The term “cartilage” refers to all forms of cartilage including, but not limited to, hyaline, elastic, and fibrocartilage.

The term “nucleic acid” or “oligonucleotide” herein refers to at least two nucleotides covalently linked together. A nucleic acid of the present invention is preferably single-stranded or double stranded and will generally contain phosphodiester bonds, although in some cases, as outlined below, nucleic acid analogs are included that can have alternate backbones, comprising, for example, phosphoramide, phosphorothioate, phosphorodithioate, O-methylphophoroamidite linkages, and peptide nucleic acid backbones and linkages. Other analog nucleic acids include those with positive backbones, non-ionic backbones, and non-ribose backbones. Nucleic acids containing one or more carbocyclic sugars are also included within the definition of nucleic acids. Modifications of the ribose-phosphate backbone can be done to facilitate the addition of additional moieties such as labels, or to increase the stability and half-life of such molecules in physiological environments.

The terms “polypeptide”, “peptide” and “protein” are used interchangeably herein to refer to a polymer of amino acid residues. The terms apply to amino acid polymers in which one or more amino acid residue is an artificial chemical analogue of a corresponding naturally occurring amino acid, as well as to naturally occurring amino acid polymers.

The term “cell adhesion molecules” refers collectively to laminins, fibronectin, vitronectin, vascular cell adhesion molecules (V-CAM) and intercellular adhesion molecules (I-CAM) and collagen.

The terms “carrier,” or “pharmaceutically acceptable carrier,” or “delivery vehicle,” or “vehicle” can be used interchangeably.

The terms “increasing”, “enhancing”, and “facilitating” may be used interchangeably.

As used herein, the term “Nell-1 peptide” can include a Nell-1 related agent. For example, a Nell-1 peptide related agent can include any polypeptide with significant homology to a Nell-1 peptide or a fragment thereof. Significant homology can be a homology of higher than about 50% homology to a Nell-1 peptide, e.g., higher than about 60% homology to a Nell-1 peptide, higher than about 70% homology to a Nell-1 peptide, or higher than about 80% homology to a Nell-1 peptide. Nell-1 peptide may be referred simply as Nell peptide herein.

The Nell-1 peptides can be natural and/or recombinant Nell-1 peptides with a non-mutated wild-type sequence or recombinant Nell-1 peptides with a mutated wild-type sequence that still contains significant homology to Nell-1 peptides. In addition, Nell-1 peptides can be derived from, but not limited to, an organism such as human cells, bacteria, yeast, or insect or plant cells. In some embodiments, the term “Nell-1 peptide” includes structural, functional or conformational equivalents of Nell-1 peptide. As used herein, a structural equivalent of a Nell-1 peptide refers to a protein or peptide including a structure equivalent or substantially similar to that of a Nell-1 peptide or of a functional domain of a Nell-1 peptide. A functional equivalent of a Nell-1 peptide refers to a protein or peptide having a function equivalent or substantially similar to that of a Nell peptide or of a functional domain of a Nell-1 peptide. A conformational equivalent of a Nell-1 peptide refers to a protein or peptide having a conformation equivalent or substantially similar to that of a Nell-1 peptide or of a functional domain of a Nell-1 peptide.

In some embodiments, the Nell-1 peptide described herein can be a derivative of the Nell-1 peptide. The term “derivative” as used herein, refers to any chemical or biological compounds or materials derived from a Nell-1 peptide, structural equivalents thereof, or conformational equivalents thereof. For example, such a derivative can include any pro-drug form, PEGylated form, or any other form of a Nell peptide that renders the Nell-1 peptide more stable or to have a better osteophilicity or lipophilicity. In some embodiments, the derivative can be a Nell-1 peptide attached to poly(ethylene glycol), a poly(amino acid), a hydrocarbyl short chain having C1-C20 carbons, or a biocompatible polymer. In some embodiments, the term “derivative” can include a Nell-1 peptide mimetics. Synthesis of mimetics of a peptide is well document in the art.

In some embodiments, the peptide derivative described herein includes a physically or chemically modified Nell-1 peptide. Physically modified peptide can be modification by, for example, modification by ionic force such as forming an ionic pair with a counterion, modification by hydrogen bonding, modification by modulation of pH, modulation by solvent selection, or modification by using different protein folding/unfolding procedures, which can involve selection of folding/unfolding temperature, pH, solvent, and duration at different stage of folding/unfolding.

In some embodiments, the peptide derivative can include a chemically modified Nell-1 peptide. For example, a short hydrocarbon group(s) (e.g. methyl or ethyl) can be selectively attached to one or multiple sites on the Nell-1 peptide molecule to modify the chemical and/or physical properties of the peptide. In some embodiments, a mono-, oligo- or poly(ethylene glycol) (PEG) group(s) can be selectively attached to one or multiple sites on the Nell-1 peptide molecule to modify the chemical and/or physical properties of the peptide by commonly known protein PEGylation procedures (see, e.g., Mok, H., et al., Mol. Ther., 11(1):66-79 (2005)).

In the same vein, isoform Nell-1 peptide can include an isoform Nell-1 related agent or derivative. The above described principles are applicable to the isoform Nell-1 peptide.

Isoform Nell-1 Peptides

Nell-1 peptide, a 810 amino acid peptide With a molecular Weight of 90 kD, has been found to have osteoinductive properties. Nell-1 peptide, methods of its expression and use in treating bone and cartilage related conditions have been described in U.S. Pat. Nos. 7,052,856 and 7,544,486, U.S. application Ser. No. 11/392,294 (issued as U.S. Pat. No. 7,776,361 B2), Ser. No. 11/594,510 (issued as U.S. Pat. No. 7,687,462 B2), Ser. No. 11/601,529 (issued as U.S. Pat. No. 7,691,607 B2), Ser. No. 11/713,366 (issued as U.S. Pat. No. 7,884,066 B2), Ser. No. 11/884,525 (issued as U.S. Pat. No. 7,833,968 B2), and Ser. No. 11/973,831.

The isoform Nell-1 in the present invention do not include the Nell-1 described in the previous patents or patent applications identified above.

Isoform Nell-1 (referred to as ISN-1 herein) is a Nell-1 peptide lacking a TSP1-N [N-terminal thrombospondin-1 (TSP-1)-like domain present in LNell-1. One exemplary ISN-1 is a short Nell-1 (SNell-1) of sequence of SEQ ID NO. 1.

Rat or mouse isoform Nell-1 peptides share ˜93% predicted amino acid homology with human Nell-1. LNell-1 contains several highly conserved motifs including a secretory signal peptide, a N-terminal thrombospondin-1 (TSP1-N)-like module (also described as laminin G-like domain), five chordin-like cysteine-rich (CR) domains (also known as von Willebrand factor type C domains) and six epidermal growth factor (EGF)-like domains. Rat LNell-1 is secreted into media as 400-kDa proteins that convert to 130-kDa proteins after prolonged denaturation. The 130-kDa monomers are assumed to associate into homotrimers via either the coiled-coil region or CR domains. The EGF-like domains interact with and are phosphorylated by protein kinase C (PKC) in a PKC isoform specific manner. (FIG. 1)

Human LNell-1 contains 810 amino acids with a molecular weight of 89.5 kD (˜120 kD after post-translational modification). LNell-1 is transcribed from the proximal alternative promoter (AP-L).

SNell-1 was predicted to have 570 aa with a molecular weight of 62.5 kD. SNell-1 is transcribed from a novel alternative promoter (AP-S). Both AP-L and AP-S contain multiple functional regulatory elements for binding Runx2 (e.g., OSE2) and Osx [e.g., specificity protein 1 (SP1)].

Runx2 promotes LNell-1 and SNell-1 mRNA/protein expression, while Osx induces SNell-1 mRNA/protein, but suppresses LNell-1 mRNA expression, indicating that LNell-1 and SNell-1 have distinct roles at early and late stages respectively of osteoblast differentiation. Moreover, LNell-1 can reciprocally downregulate Osx transcription, while SNell-1 can upregulate both Runx2 and Osx transcripts and increases osteoblastic differentiation. Like LNell-1, SNell-1 is expressed during skeletal growth and demonstrates osteogenic potential in vitro and in vivo.

Both Nell-1 isoforms can be required during osteogenesis. LNell-1 and SNell-1 have distinct, non-overlapping functions during osteogenesis and chondrogenesis. SNell-1, which upregulates both Runx2 and Osx, is believed to be an even more potent osteoinductive agent than LNell-1.

SNell-1 peptide is of a sequence of SEQ ID NO. 1. SNell-1 peptide is encoded by a DNA sequence of SEQ ID NO. 2. LNell-1 peptide is of a sequence of SEQ ID NO. 3. LNell-1 peptide is encoded by a DNA sequence of SEQ ID NO. 4.

Method of Increasing Bone Formation and Regeneration

This invention provides a method of increasing bone formation and regeneration. The method can be used for bone fracture repair. The method is useful in a variety of contexts including, but are not limited to, bone reconstruction of defects occurring as a result of trauma, cancer surgery or errors in development, treatment of osteogenesis imperfecta, treatment of osteoporosis, and the healing of major or minor bone fractures.

The method for bone fracture repair comprises increasing concentration of an ISN-1 gene product at or near the fracture site. In some embodiments, the method comprises transfecting an osteogenic cell with a vector that expresses ISN-1 protein or a related agent at or near the bone fracture site. In some embodiments, the method comprises introducing an osteogenic cell or bone precursor cell that overexpresses ISN-1 into the fracture site.

In another approach to fracture repair, the fracture site is contacted with an ISN-1 protein. In some embodiments, the fracture site is contacted with LNell-1 in addition to an ISN-1 protein. The protein can be produced by a cell (e.g. introduced by introduction of a cell overexpressing Nell-1 protein), or by administration of the protein alone or in combination with a pharmacological excipient, or by administration of a “naked DNA” vector capable of expressing Nell-1 peptide or the ISN-1. The ISN-1 protein can be a component of a bone repair/bone graft material and/or part of a prosthetic device.

In some embodiments, in a manner analogous to the use of bone morphogenic proteins (e.g. BMP-1 through BMP-24), the ISN-1 can be used to speed repair of bone fractures or to induce bone repair or replacement under circumstances where natural healing is limited or non-existent. In generally such methods involve increasing the amount of a Nell-1 gene product at or near the fracture site in a bone. The ISN-1 gene product concentration can be increased by one or more of a number of methods. In one approach, cells at or near the bone fracture site are induced to express elevated levels of ISN-1. This can be accomplished in vivo, for example, by the use of modulators of Nell-1 expression, by altering the ISN-1 promoter, or by transfecting the cell with a construct that expresses ISN-1. This also can be accomplished by modifying such cells to overexpress Nell-1 ex vivo and then introduced back into the subject organism (e.g. at or near a fracture site).

In various embodiments, this invention provides a method of facilitating bone formation or regeneration, the method comprising increasing the concentration of an ISN-1 gene product in an osteogenic cell. The ISN-1 gene product can be an ISN-1 peptide, a related agent, or a combination thereof. In some embodiments, the osteogenic cell can be a mature osteoblast, osteoblast, a mesenchymal cell, a fibroblast cell, a fetal embryonic cell, a stem cell, a bone marrow cell, a dura cell, a chrondrocyte, and a chondroblast.

In some embodiments, the increasing concentration of an ISN-1 gene product comprises transfecting an osteogenic cell with a vector that expresses an ISN-1 protein or a related agent. In some embodiments, the increasing concentration of an ISN-1 gene product comprises administering to the bone fracture site with a composition comprising an ISN-1 protein or a related agent. The composition can further comprise a pharmaceutically acceptable carrier.

In various embodiments, the use of ISN-1 and LNell-1 can be combined. It is expected that ISN-1 and LNell-1 can work in synergy and the combination provides improvement to the existing approaches.

In various embodiments, the isoform Nell-1 can be SNell-1.

Method of Treating Osteoporosis

The use of Nell-1 for treating, preventing, and ameliorating osteoporosis has been described in U.S. application Ser. No. 11/713,366 (issued as U.S. Pat. No. 7,884,066 B2), the teaching of Which is incorporated by reference herein.

In various embodiments, this invention provides a method of treating, preventing or ameliorating osteoporosis by administering to a bone tissue at a pre-selected site an effective amount of an ISN-1 or related agent.

In some embodiments, the method can further comprise applying to the pre-selected site a physical force to disperse the ISN-1 or related agent. In some embodiments, the physical force can be ultrasound.

In some embodiments, the administering step comprises: making an incision in the bone tissue at the pre-selected site, and delivering to the bone tissue at the pre-selected site via the incision.

In some embodiments, the ISN-1 or related agent is formulated into a formulation suitable for a mode of delivery selected from percutaneous injection through intact skin to a site, direct injection through a surgically opened site or a trauma site, surgical implantation, extravascular delivery, extravascular injection, extravascular catheter based injection, intravascular delivery, intravascular injection, intravascular catheter based injections, intravenous delivery, intravenous injection, intravenous catheter based injections, intraarterial delivery, intraarterial injection, intraarterial catheter based injections, intrathecal delivery, intrathecal injection, intrathecal catheter based injections, intraosseous delivery, intraosseous injection, catheter based injections, intracartilaginous delivery, intracartilaginous injection, intracartilaginous catheter based injections, intravesical delivery, intravesical injection, intravesical catheter based injection, delivery via a mechanical pump with a percutaneous or implantable catheter, catheter based delivery to an area or organ in the body, or delivery via expanded dispersion through a device that increases tissue penetration or wider tissue distribution. In some embodiments, the device provides ultrasound, iontophoresis, heat or pressure.

In various embodiments, the use of ISN-1 and LNell-1 can be combined. It is expected that ISN-1 and LNell-1 can work in synergy and the combination provides improvements to the existing approaches. In various embodiments, the isoform Nell-1 can be SNell-1.

Method of Inducing Cartilage Formation and Regeneration

The use of Nell-1 for inducing cartilage formation and regeneration has been described in U.S. application Ser. No. 11/594,510, the teaching of which is incorporated by reference herein.

In various embodiments, the present invention provides agents and methods for inducing cartilage formation or repair using an ISN-1 peptide or a related agent (collectively referred as “agent”). The composition can include an ISN-1 peptide, a related agent, and optionally at least one other active agent, cells, and biocompatible material implanted for the purpose of cartilage repair (i.e., hyaline cartilage, elastic cartilage, or fibrocartilage).

In some embodiments, the present invention provides a composition that contains an effective amount of at least one agent for either directly or indirectly promoting the generation of cartilage for treating, preventing or ameliorating a cartilage related medical condition. One of the agents for direct promotion of cartilage generation can be ISN-1 peptides or ISN-1 based gene therapy or ISN-1 gene product enhancers applied to chondrogenic cells such as, but not limited to, chondroblasts, chondrocytes, or chondroprogenitor cells, adult and embryonic stem cells, bone marrow cells, bone marrow stromal cells, mesenchymal cells, a fibroblast, or adipose derived cells. The agent for indirect promotion of cartilage generation (e.g., through inducing chondroblast/chondrocyte differentiation) can be, e.g., one of Nell peptide, or agonists of Nell peptide receptors.

In some embodiments, the composition can include, e.g., one or more inhibitors or antagonists of ISN-1 peptide receptors, high dose ISN-1 peptides, or combinations thereof. Such a composition is effective for inhibition of chondrogenic differentiation by inhibiting potential or committed chondrogenic cells such as, but not limited to, osteoblasts, osteoprogenitor cells, stem cells, bone marrow cells, fibroblastic cells, dural cells, periosteal cells, pericytes, and/or muscle cells.

In various embodiments, the use of ISN-1 and LNell-1 can be combined. It is expected that ISN-1 and LNell-1 can work in synergy and the combination provides improvements to the existing approaches. In various embodiments, the isoform Nell-1 can be SNell-1.

Composition

In various embodiments, this invention provides a composition useful for facilitating bone formation or regeneration. The composition comprises an ISN-1 peptide, an ISN-1 related agent, or a combination thereof.

The composition can be a pharmaceutical composition which comprises a pharmaceutically acceptable carrier. The pharmaceutically acceptable carrier can be a carrier for a mode of delivery of oral administration, topical administration, in situ implant, intravenous administration, parenteral administration, local administration, intra-arterial injection, injection into a fracture site, and delivery in a biodegradable matrix. In the various embodiments, the composition can further comprise LNell-1 protein, a related agent, or a combination thereof.

The pharmaceutical composition can be formulated into a formulation suitable for a mode of delivery selected from percutaneous injection through intact skin to a site, direct injection through a surgically opened site or a trauma site, surgical implantation, extravascular delivery, extravascular injection, extravascular catheter based injection, intravascular delivery, intravascular injection, intravascular catheter based injections, intravenous delivery, intravenous injection, intravenous catheter based injections, intraarterial delivery, intraarterial injection, intraarterial catheter based injections, intrathecal delivery, intrathecal injection, intrathecal catheter based injections, intraosseous delivery, intraosseous injection, catheter based injections, intracartilaginous delivery, intracartilaginous injection, intracartilaginous catheter based injections, intravesical delivery, intravesical injection, intravesical catheter based injection, delivery via a mechanical pump with a percutaneous or implantable catheter, catheter based delivery to an area or organ in the body, or delivery via expanded dispersion through a device that increases tissue penetration or wider tissue distribution.

In various embodiments, the use of ISN-1 and LNell-1 can be combined. ISN-1 and LNell-1 can be used in the same fashion or substantially the same fashion. It is expected that ISN-1 and LNell-1 can work in synergy and the combination provides improvements to the existing approaches. In various embodiments, the isoform Nell-1 can be SNell-1.

Bone Graft

In various embodiments, the composition can be a bone graft material. In various embodiments, this invention provides a bone graft material for enhancing bone formation in the animal in which it is implanted.

In some embodiments, the bone graft material contains a biocompatible matrix and an ISN-1 protein, a related agent, or a combination thereof. In some embodiments, the graft material can be resorbable or biodegradeable or biostable. In some embodiments, the graft material can be synthetic or naturally occurring (e.g., allograft). The matrix can include a biodegradable polymer or a biostable polymer and can be impregnated with an ISN-1 protein, a related agent, and/or a cell expressing an ISN-1 protein or a related agent. The biocompatible matrix can comprise collagen. The biocompatible matrix can comprise a bioglass or a bioceramics. The biocompatible matrix can comprise a cell adhesion molecule.

In some embodiments, the ISN-1 protein is produced by a cell within the matrix expressing the ISN-1 protein or a related agent, which are exogenous. In some embodiments, the ISN-1 protein is provided via pharmaceutical composition. In the aforementioned embodiments, the bone graft material can further comprise LNell-1 protein, a related agent, or a combination thereof.

An exemplary bone graft material comprises a collagen conjugate containing (e.g. from about 0.001 to about 99.999 weight percent) collagen having dispersed substantially uniformly therein; and (e.g. about 99.999 to about 0.001 weight percent) an ISN-1 protein, a related agent, and/or a cell expressing an ISN-1 protein or a related agent. In some embodiments, the graft material includes collagen and/or demineralized or non-demineralized bone fragments in addition to the ISN-1 protein or cells expressing an ISN-1 protein.

Cells expressing or over expressing ISN-1 can be incorporated into such bone graft materials or ISN-1 polypeptides can be incorporated into such bone graft materials. These graft materials can be used in the treatment of fractures or to facilitate the replacement/healing of prostheses or bone transplants.

In various embodiments, the use of ISN-1 and LNell-1 can be combined. It is expected that ISN-1 and LNell-1 can work in synergy and the combination provides improvements to the existing approaches. In various embodiments, the isoform Nell-1 can be SNell-1.

Method of Making Isoform Nell-1 Peptide

The expression and purification of Nell-1 peptide has been described in U.S. Pat. No. 7,544,486 and Us. application Ser. No. 11/601,529 (issued as U.S. Pat. No. 7,691,607 B2), the teachings of Which are incorporated by reference herein.

This invention provides methods for the expression and purification of the isoform Nell-1. In various embodiments, this invention provides nucleic acid constructs expressing ISN-1 and cells expressing ISN-1 peptides which may be useful in producing quantities of ISN-1 peptides. In some embodiments, the nucleic acid constructs expressing ISN-1 may further include nucleic acid sequences encoding signal peptides which may facilitate the protein trafficking and post production modification of the ISN-1 in the host cell. In some embodiments, the signal peptide may facilitate the secretion of the peptide from the host cell.

In various embodiments, this invention provides a method of expressing a functional ISN-1 peptide in a cell, said method comprising: providing a nucleic acid construct including at least a nucleic acid encoding at least a ISN-1 peptide in frame with a nucleic acid encoding a secretory signal peptide; transfecting a cell with said nucleic acid construct; culturing said cell under conditions that permit expression of the ISN-1 peptide; optionally collecting ISN-1 peptide secreted from the cell line; optionally substantially purifying the ISN-1 peptide; and optionally testing the activity of the ISN-1 peptide to induce bone formation.

In various embodiments, this invention provides a nucleic acid construct for expressing an ISN-1 peptide in a cell, said nucleic acid construct comprising at least a nucleic acid encoding at least an ISN-1 peptide in frame with a nucleic acid encoding a secretory signal peptide.

In various embodiments, this invention provides a cell line for expressing a functional ISN-1 peptide, said cell line including a nucleic acid construct comprising at least a nucleic acid encoding at least an ISN-1 peptide in frame with a nucleic acid encoding a secretory signal peptide.

In some embodiments, the secretory signal peptide is an insect secretory peptide. In some embodiments, the secretory signal peptide is a Nell peptide signal sequence. In some embodiments, the secretory signal peptide is selected from the group consisting of a melittin signal sequence, a drosphila immunoglobulin-binding protein signal sequence, an equine interferon-gamma (elFN-gamma) signal peptide, a snake phospholipase A2 inhibitor signal peptide, a human lysozyme signal peptide, and a chicken lyzozyme signal peptide.

In the aforementioned embodiments, the cell can be a mammalian cell or an insect cell. Said insect cell can be a high five cell. Said mammalian cell can be a COS7 cell. In the aforementioned embodiments, the secretory signal peptide can be a Nell peptide signal sequence. In the aforementioned embodiments, the ISN-1 peptide can be SNell-1.

In various embodiments, the isoform Nell-1 can be SNell-1.

U.S. Pat. Nos. 7,052,856 and 7,544,486, and U.S. application Ser. No. 11/392,294 (issued as U.S. Pat. No. 7,776,361 B2), Ser. No. 11/594,510 (issued as U.S. Pat. No. 7,687,462 B2), Ser. No. 11/601,529 (issued as U.S. Pat. No. 7,691,607 B2), Ser. No. 11/713,366 (issued as U.S. Pat. No. 7,884,066 B2), and Ser. No. 11/973,831 describe Nell-1 peptide, compositions thereof, its expression and purification, and its use in bone fracture repair including facilitating bone formation and increasing bone mineralization, treating osteoporosis, and inducing cartilage formation and regeneration. These patents or applications provide the state of art which contributes to the enablement to various aspects of the present invention.

Embodiments

The method of bone formation and repair generally involves increasing ISN-1 protein concentration in a bone progenitor cell or contacting a cell (e.g. a bone progenitor cell) with an ISN-1 polypeptide or with a vector encoding an ISN-1 polypeptide.

This can be accomplished by transforming a bone precursor cell so that it expresses elevated levels of endogenous ISN-1 or so that it expresses ISN-1 from an exogenous transfected ISN-1 nucleic acid.

This also can be accomplished by contacting bone precursor cells at or near the bone, bone fracture site, or cartilage disease site with an ISN-1 protein or a composition thereof or local administration of an ISN-1 protein or a composition thereof.

A) Transformation of Cells to Increase ISN-1 Production.

In a more preferred embodiment, the ISN-1 gene expressing nucleic acids (e.g. cDNA(s)) can be cloned into gene therapy vectors that are competent to transfect cells (such as human or other mammalian cells) in vitro and/or in vivo. The methods and procedures of such cloning and cell transfection are described in U.S. application Ser. No. 09/412,297, filed on Oct. 5, 1999, the teachings of which are incorporated herein in their entirety by reference.

B) Administration of Exogenously Produced ISN-1

1) Delivery of ISN-1 to Target Cells

ISN-1 proteins or related agents can be prepared for intravenous, parenteral, topical, oral, or local administration (e.g. by aerosol or transdermally). Particularly preferred modes of administration include intra-arterial injection, injection into fracture sites or delivery in a biodegradable matrix. The ISN-1 proteins agents can be combined with a pharmaceutically acceptable carrier, which can be referred to as carrier or excipient, to form a pharmacological composition.

Various pharmaceutically suitable formulations, carriers, other additives, and administering routes are described in US. application Ser. No. 11/392,294 (issued as U.S. Pat. No. 7,776,361 B2), Ser. No. 11/713,366 (issued as U.S. Pat. No. 7,884,066 B2), Ser. No. 11/884,525 (issued as U.S. Pat. No. 7,833,968 B2), and Ser. No. 11/973,831, Which are incorporated herein by reference.

2) Bone Graft Materials

ISN-1 protein can be applied directly to a bone or bone fracture site. This can be accomplished during surgery (e.g. when setting complex fractures, when reconstructing bone, when performing bone transplants, etc.) or can be accomplished by direct injection.

In certain preferred embodiments, particularly bone reconstruction or repair is performed surgically, it is desired to administer the ISN-1 protein using a sustained delivery “vehicle”. Sustained delivery vehicles include, but are not limited to biodegradable delivery vehicles. Biodegradable delivery vehicles are preferably porous. Various delivery vehicles are described in US. application Ser. No. 11/392,294 (issued as U.S. Pat. No. 7,776,361 B2), Ser. No. 11/713,366 (issued as U.S. Pat. No. 7,884,066 B2), and Ser. No. 11/884,525 (issued as U.S. Pat. No. 7,833,968 B2), Ser. No. 11/973,831, which are incorporated herein by reference.

Other delivery vehicles include, but are not limited to bone graft materials. Bone graft materials can be derived from natural materials (e.g. transplanted bone or bone fragments), synthetic materials (e.g. various polymers and/or ceramics) or combinations of both. Bone graft materials are typically utilized to fill voids or otherwise replace lost bone material. Such graft materials are also often provided as components of prosthetic devices (e.g. bone replacements or supports) to facilitate tight bonding/annealing of the prosthetic with the living bone. The bone graft material can include a biodegradable polymer or a biostable polymer.

Bone grafts using bioactive glasses and calcium phosphates, collagen, mixtures and the like have good biocompatibility and give rise to bone tissue formation and incorporation in some cases. Various bone graft materials are described in US. application Ser. No. 11/392,294 (issued as U.S. Pat. No. 7,776,361 B2), Ser. No. 11/713,366 (issued as U.S. Pat. No. 7,884,066 B2), and Ser. No. 11/973,831, which are incorporated herein by reference.

The bone graft material can further include bone morphogenic proteins (BMP) or other bioactive agents such as cell adhesion molecules. Particularly suitable graft materials include, for example, isolated mineralized cancellous bone sections, powders or granules of mineralized bone, demineralized cancellous bone sections, powders or granules of demineralized bone, guanidine-HC1 extracted demineralized bone matrix, sintered cortical or cancellous bone, coralline hydroxyapatite sold by Interpore under the trade name Interpore 500, and granular ceramics such as that incorporated into the bone graft substitute Collagraft sold by Zimmer, or filamentous sponges such as those made from collagen by Orquest.

In various embodiments, the ISN-1 proteins, BMP, or other bioactive agent can be bound to the substrate of the bone graft materials.

3) ISN-1 for Osteoporosis

In some embodiments, the ISN-1 protein described herein can be used to treat, prevent, or ameliorate osteoporosis. In this embodiment, the ISN-1 peptide can be administered to a site of osteoporosis. Subsequently, a physical force such as a vibration or ultrasound can be applied to the site of administration to disperse the ISN-1 peptide. In some embodiments, the ISN-1 peptide can be administered to the site of osteoporosis by the acts of (a) making an incision in a tissue (bone) and (b) delivering to the tissue through the incision the ISN-1 peptide. In some embodiments, the Nell-1 peptide can be in a pharmaceutically acceptable carrier for sustained delivery.

4) ISN-1 for Cartilage Regeneration

In the present invention, the isoform Nell-1 peptide can be used to treat, prevent, or ameliorate cartilage degeneration. In one embodiment, the ISN-1 peptide can be administered to a site of fibrocartilage disease such as spinal disc disease with or without a pharmaceutically acceptable carrier, with or without other devices (e.g., disc nucleus replacement device, allograft device, or cells) or biological factors (e.g., LIM-1 protein). In another embodiment, the ISN-1 peptide can be administered to a site of fibrocartilage disease such as meniscus, with or without a pharmaceutically acceptable carrier, with or without other devices (e.g., meniscus allograft or meniscus scaffold or prosthesis, or cells) or biological factors. In another embodiment, the SNell-1 peptide can be administered to a site of hyaline cartilage disease such as knee articular cartilage, with or without a pharmaceutically acceptable carrier, with or without other devices (e.g., cartilage allograft or cartilage scaffold or prosthesis) or biological factors. In another embodiment, the ISN-1 peptide can be administered to another site of hyaline cartilage disease such as tracheal cartilage (e.g., tracheomalacia), with or without a pharmaceutically acceptable carrier, with or without other devices (e.g., cartilage allograft or cartilage scaffold or prosthesis) or biological factors.

In other embodiments, the ISN-1 peptide can be administered to a site of elastic cartilage disease such as auricular or epiglottis with or without a pharmaceutically acceptable carrier, with or without other devices (e.g., cells) or biological factors.

A composition described herein can be formulated into formulations suitable for any suitable mode of administration/delivery to a mammalian subject (e.g., a human being). An ordinary artisan with the teachings above can formulate the composition described here into any desirable formulation by using, e.g., an appropriate carrier with an appropriate amount of an ISN-1 peptide or a related agent defined above.

Some examples of delivering the composition can be, e.g., percutaneous injection through intact skin to various sites, or direct injection through nonintact skin (e.g., surgically opened sites or trauma sites). In some embodiments, the delivery can be surgical implantation of a composition described herein. In some embodiments, the delivery can be one of extravascular delivery, injection or catheter based injections; intravascular delivery, injection or catheter based injections; intravenous delivery, injection or catheter based injections; intraarterial delivery, injection or catheter based injections; intrathecal delivery, injection or catheter based injections; intraosseous delivery, injection or catheter based injections; intracartilaginous delivery, injection or catheter based injections; or intravesical delivery, injection or catheter based injections.

In some embodiments, a delivery of composition described herein to a mammalian subject can be delivery via mechanical pumps with percutaneous or implantable catheters. In some embodiments, a delivery of composition described herein to a mammalian subject can be catheter based delivery to any area/organ in the body.

In some embodiments, a delivery of composition described herein to a mammalian subject can be delivery via expanded dispersion through various devices promoting increased tissue penetration or wider tissue distribution (e.g., ultrasound, iontophoresis, heat, pressure, etc.)

EXAMPLES

The following example illustrates, but not to limit the claimed invention.

1. SNell-1

An optional open reading frame in exon 7 within 240 amino acids from the first open reading frame (ORF) that lacks the TSP1-N like domain in silico search was identified. The ATG potential translational start site for SNell-1 site is located within exon 7 of LNell-1 and the promoter sequences for SNell-1 are within intron 2 of LNell-1. Based on 5′ RACE and sequencing results, the existence of the predicted short form was further demonstrated. Independent work by Database of Transcriptional Starting Sites (http://dbtss.hgc.jp) using 5′ Oligo-Capping method also identified a clone with the same alternative form for SNell-1.

SNell-1 5′ primer was designed based on its 5′ UTR sequence. When transfected with Osx, the PCR product using N-terminal primers (specific for LNell-1) was significantly downregulated (coinciding with the promoter result), while the PCR product using SNell-1 specific primers was significantly elevated above control (FIG. 2). In contrast, Runx2 transfection upregulated both LNell-1 and SNell-1 transcripts.

LNell-1 contains 810 aa with a molecular weight of 89.5 kD (˜120 kD after post-translational modification); the predicted size for SNell-1 is 570 aa with a molecular weight of 62.5 kD.

To further verify the existence of this smaller isoform, the media from Osx transfected NMCCs was collected. It was shown that Osx downregulated LNell-1 and increased the expression of an ˜70 kD SNell-1 protein that is consistent with the predicted nonglycosylated weight of 62.5 kD (FIG. 2). Similar results were obtained using Saos2 cells.

2. Functional Role of SNell-1 in Skeletal Development

A Nell-1 gene-trapped ES cell line was used to generate general and tissue specific [Col1α1-Cre-(osteoblastic) and Col2α1-Cre (chondrogenic)] Nell-1 knockouts. LNell-1 and SNell-1 overexpressing mice were generated. In addition to comprehensive morphological and histological examination, levels of Runx2 and Osx expression were further examined on the different Nell-1 expression backgrounds by immunohistochemistry.

Given the important roles of Runx2 and Osx during skeletal development, SNell-1's effect on Runx2 and Osx expression were studied. Because phosphorylation status can affect Runx2 and Osx activity and because LNell-1 has been demonstrated to increase Runx2 phosphorylation and activity, SNell-1's effects on Runx2 and Osx phosphorylation status and activity were studied.

SNell-1 is normally expressed by late-stage osteoblasts. Excessive SNell-1 may induce more significant cellular apoptosis and greater inhibition of cell proliferation than LNell-1, with accelerated bone formation relative to WT mice, but decreased total bone formation relative to LNell-1 overexpression mice.

In terms of chondrogenesis, SNell-1 (which Runx2 and Osx upregulates and which reciprocally upregulates Runx2 and Osx mRNA) promotes early chondrocyte differentiation, with possible inhibitory effects on terminal chondrocyte differentiation.

The differential effects of LNell-1 vs. SNell-1 in Saos-2 cells were examined Saos-2 transfected with pcDNA3.1-SNell-1 demonstrated increased Runx2, Osx, and Oc expression by day 6 of culture. In contrast, LNell-1 transfected Saos-2 cells demonstrated no change in Runx2 transcription (consistent with our previous data in MC3T3-E1), transiently increased Oc expression, and marked decrease in Osx expression (FIG. 3).

FIG. 3 shows the effects of LNell-1 and SNell-1 on Runx2, Osx, Oc expression and mineralization. FIG. 3(A) shows that Saos2 cells were transfected with pcDNA3.1 (Control), pcDNA3.1-LNell-1 or -SNell-1 for 24 hours and then exposed to osteogenic differentiation medium. mRNA expression of Runx2, Osx and Oc was analyzed by real-time PCR. *p<0.05, **p<0.01 compared to data of day 1 within same group. #p<0.05, ##p<0.01 compared to control group within same time point. FIG. 3(B) shows Lentiviral transfection. Both LNELL-1 and SNell-1 show significant mineralization compared to control. #p<0.05.

SNell-1 was expressed during skeletal growth (FIG. 4) and formed bone when applied to calvarial defects (FIG. 5). FIG. 4 shows LNell-1 and SNell-1 protein express patterns in mice heads. LNell-1 is known to be highly expressed in brain tissues and is consistently expressed during and after gestation while SNell-1 is predominantly expressed postnatally.

FIG. 5 shows Calvarial defect healing with SNell-1. SNell-1 lentivirus (5M virus particles per site) embedded in collagen coated PLGA scaffolds were implanted onto 3 mm calvarial defect in athymic rats. Live μCT were taken at 2 weeks and high resolution μCT taken at 4 weeks. BV/TV and bone surface density both showed that SNell-1 induced significantly more bone formation (*p<0.05).

These data demonstrate that SNell-1 exhibits potent osteoinductive capability. It was found that isoform Nell-1 peptides are required for normal skeletal development and that isoform Nell-1 peptides are key components in the Runx2 and Osx regulatory network controlling osteoblastogenesis and terminal chondrocyte differentiation.

LNell-1 may be involved in earlier-stage and SNell-1 in later-stage osteoblastogenesis, and the converse for chondroblastogenesis (i.e., LNell-1 may be involved in later-stage; SNell-1 in earlier-stage). LNell-1 (upregulated by Runx2 and downregulated by Osx) may promote earlier stage osteoblast differentiation and less mature bone formation, while SNell-1 (upregulated by Osx and Runx2) may promote later stage osteoblast differentiation and more mature bone formation.

Conversely, for chondrocytes, Runx2 upregulated LNell-1 may promote terminal chondrocyte maturation (given the known roles of Runx2 in promoting chondrocyte hypertrophy) and Osx/Runx2 upregulated SNell-1 may have minimal or perhaps even inhibitory effects on terminal chondrocyte differentiation (given the known inhibitory effects of Osx on chondrocyte hypertrophy).

These data suggests that SNell-1 can lead to safer and more effective osteoinductive therapies.

3. Isoform Nell-1's Effects on Runx2 and Osx Phosphorylation and Activity

Coordinated regulation of Runx2 and Osx activity are crucial for bone formation. Studies by the present inventors suggest that LNell-1 and SNell-1 are important, not only as target genes for carrying out Runx2 and Osx functions, but that LNell-1 and SNell-1 are important for modulating Runx2 and Osx expression and activity during cell differentiation. Understanding of isoform Nell-1's function and mechanism will lead to improved and safer therapeutic approaches to conditions related to bone formation.

The effects of isoform Nell-1 on Runx2 phosphorylation status were examined and correlated with Runx2 activity. Runx2 activity was quantitated physiologically by osteoblastic marker expression, and directly by luciferase reporter systems that serve as direct readouts of Runx2 activity.

Because LNell-1 increases Runx2 phosphorylation through involvement of mitogen-activated kinase signaling (MAPK) cascades, and contains a conserved TSP1-N/LG-like domain that may interact with cell-surface integrins to activate MAPK pathways, the relative levels of MAPK and focal adhesion kinase (FAK) activation by LNell-1 and SNell-1 were also examined.

LNell-1 and SNell-1 exerted different effects on Runx2 and Osx phosphorylation and activity with correspondingly different effects on osteogenic and chondrogenic differentiation.

The effects of single or combined Nell-1 isoforms on Runx2 and Osx phosphorylation status and corresponding bioactivities were also examined Combined LNell-1 and SNell-1 can synergistically increase Runx2 activity and osteoblast differentiation and therefore provide a combined therapies.

4. Isoform Nell-11 Effects on Bone Formation In Vivo

The osteoinductivity of LNell-1 and SNell-1 in a calvarial defect model and a bone marrow stem cell (BMSC) implant model were examined.

Both Runx2 and Osx are known to promote osteoblast lineage commitment and maturation. However, while Runx2 promotes terminal chondrocyte differentiation, Osx inhibits this process. Osx-induced SNell-1 will preferentially promote an intramembranous ossification-like process of direct osteogenesis (i.e., mesenchymal stem cells differentiating into osteoblasts), while LNell-1, which is specifically upregulated by Runx2 and downregulated by Osx, can preferentially promote a more endochondral ossification-like process of step-wise osteogenesis (e.g., mesenchymal stem cells differentiating into chondrocytes with formation of calcified matrix, followed by vascular invasion and influx of new mesenchymal stem cells that then differentiate into osteoblasts).

It is expected that combined LNell-1 and SNell-1 therapies are more efficacious for bone growth at lower doses—allowing further optimization of Nell-1 safety and efficacy. The BMSC study will also determine how to use the two isoform Nell-1 peptides as novel molecular tools to control bone vs. cartilage formation in healing bone fractures so that development of excessive cartilage in the fracture callus can be minimized and direct, or step-wise, bone formation maximized.

To determine the relative osteoinductive and chondroinductive properties of LNell-1 vs. SNell-1 vs. combination LNell-1/SNell-1 in complex in vivo environments, two models were used—an established calvarial defect model of intramembranous bone regeneration that does not form chondroid bone and a BMSC implantation model that more closely resembles endochondral bone regeneration with osteochondral bone formation. Quantitative and qualitative bone formation was evaluated at gross morphologic, histologic, and molecular levels.

The osteoinductive properties of rhLNell-1 vs. rhSNell-1 in an intramembranous ossification model were studied. Previous data indicates that LNell-1 can accelerate both chondrogenesis and osteogenesis. In contrast, SNell-1, unlike LNell-1, can primarily promote osteoblastogenesis with minimal (or perhaps even inhibitory effects) on terminal chondrocyte differentiation. It is expected that SNell-1 will induce faster and more mature bone which manifests as increased bone volume/density, increased or earlier expression of osteoblastic marker genes, and/or more mature bone trabecular patterns on histology. 

The invention claimed is:
 1. A composition, comprising an isoform Nell-I peptide (ISN-1) consisting of the amino acid sequence according to SEQ ID NO: 1, wherein the ISN-1 is PEGylated, impregnated in a synthetic matrix or synthetic bone graft material, or a component of a prosthetic device.
 2. The composition of claim 1, further comprising a pharmaceutically acceptable carrier.
 3. The composition of claim 1, further comprising LNell-1 protein.
 4. The composition of claim 2, wherein the pharmaceutically acceptable carrier is suitable for a mode of delivery selected from the group consisting of oral administration, topical administration, in situ implant, intravenous administration, parenteral administration, local administration, intra-arterial injection, injection into a fracture site, and delivery in a biodegradable matrix.
 5. The composition of claim 1, which is formulated into a formulation suitable for a mode of delivery selected from percutaneous injection through intact skin to a site, direct injection through a surgically opened site or a trauma site, surgical implantation, extravascular delivery, extravascular injection, extravascular catheter based injection, intravascular delivery, intravascular injection, intravascular catheter based injections, intravenous delivery, intravenous injection, intravenous catheter based injections, intraarterial delivery, intraarterial injection, intraarterial catheter based injections, intrathecal delivery, intrathecal injection, intrathecal catheter based injections, intraosseous delivery, intraosseous injection, catheter based injections, intracartilaginous delivery, intracartilaginous injection, intracartilaginous catheter based injections, intravesical delivery, intravesical injection, intravesical catheter based injection, delivery via a mechanical pump with a percutaneous or implantable catheter, catheter based delivery to an area or organ in the body, or delivery via expanded dispersion through a device that increases tissue penetration or wider tissue distribution.
 6. The composition of claim 1, wherein the composition is a synthetic bone graft comprising a biocompatible matrix and the ISN-1.
 7. The composition of claim 6, wherein the ISN-1 is produced by a cell within the matrix expressing the ISN-1 which is exogenous.
 8. The composition of claim 6, wherein the biocompatible matrix is resorbable.
 9. The composition of claim 6, wherein the biocompatible matrix comprises a biodegradable polymer or a biostable polymer.
 10. The composition of claim 6, wherein the biocompatible matrix comprises a cell adhesion molecule.
 11. A method of forming a composition according to claim 1, comprising: providing the ISN-1, and forming the composition comprising the ISN
 1. 12. The composition of claim 1, wherein the synthetic matrix comprises bioglass or bioceramics.
 13. The composition of claim 1, wherein the pharmaceutically acceptable carrier comprises a polymer.
 14. The composition of claim 2, wherein the pharmaceutically acceptable carrier comprises a sustained release vehicle. 